Analysis of the hydrodynamic effect on the load capacity and rotational accuracy of hydrostatic spindle

Purpose This study aims to quantifying the effects of hydrodynamic forces on spindle performance under eccentric and rotational conditions, which can impact load capacity and rotational accuracy, ultimately affecting the machining precision of machine tools. Design/methodology/approach This study investigates the fluid dynamics performance of bearings by analyzing the effect of fluid dynamic pressure on the rotor’s rotational trajectory. First, the Reynolds equation is solved using the finite difference method, and the pressure distribution of the bearing is calculated based on the principle of mass flow conservation. Subsequently, the rotor’s rotational trajectory at the center is further calculated using Newton’s law of motion. To more efficiently describe the fluid dynamic pressure effect, this study utilizes the uniform pressure phenomenon at the sealing edges during the static effect to effectively distinguish the pressure distribution of the fluid dynamic pressure effect from the overall pressure distribution of the bearing. Finally, the method is used to analyze the interrelationship between the pressure distribution of the fluid dynamic pressure effect and the rotor’s rotational trajectory. Findings The results indicate that as spindle speed increases from 0 rpm, the liquid dynamic pressure effect on the spindle likewise increases. The rate of increase in dynamic pressure effects surpasses that of hydrostatic effects at higher speeds. Furthermore, higher spindle speeds correspond to reduced rotor displacement during the transition from an unsteady to a steady state, resulting in improved rotational accuracy. Originality/value To the best of the authors’ knowledge, this study is the first to employ the rotor rotational trajectory method to quantitatively analyze the effect of dynamic pressure on bearing performance under various bearing design and operational parameters. Through a systematic analysis of the effects of these parameters on bearing performance, the study not only provides new insights for optimizing oil film characteristics but also effectively reduces system vibrations and thermal deformation. This research provides an important theoretical foundation for bearing design and optimization and has far-reaching practical implications for improving the overall performance of high-precision rotating systems.